WASHINGTON (CNN) -- A conservative majority of the Supreme Court appeared ready Wednesday to support an Indiana law requiring voters to show photo identification, despite concerns that it could deprive thousands of people of their right to vote.

The Supreme Court is reviewing an Indiana law that requires voters to show a photo ID.

At issue is whether state laws designed to stem voter fraud would disenfranchise large numbers of Americans who might lack proper identification -- many of them elderly, poor or minority voters.

In what has become a highly partisan legal and political fight, the justices wrestled with a balancing test of sorts to ensure both state and individual interests were addressed.

Civil rights activists and the state Democratic Party complain Indiana's law is the most restrictive in the nation.

"The real question is, does it disenfranchise anyone?" Todd Rokita, Indiana secretary of state told CNN. "After six elections in the state of Indiana, the answer has been no. ... That's why the opponents to this keep losing in court."

State officials claim that voter turnout actually has increased 2 percent since the law took effect. But Rokita concedes the state has never presented a case of "voter impersonation," which the law was designed to safeguard against.

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Justice Samuel Alito spoke for many of his colleagues, wondering how they should rule in the absence of any clear evidence supporting either side.

"The problem I have is, where do you draw the line?" he said. "There is nothing to quantify the extent of the problem or the extent of the burden."

Among those cited by Democrats is Mary-Jo Criswell, a 71-year-old Indianapolis Democrat, who could not vote last November because she had no driver's license or valid passport.

She previously had used a private bank-issued card with her photo when voting. The former precinct committeewoman had difficulty rebuilding an identity trail, and still does not have a valid photo ID. Criswell said in an affidavit she felt intimidated by the burdensome bureaucracy she claims is needed to vote.

This is perhaps the biggest voter rights case taken up by the justices since the 2000 dispute over Florida's ballots, where George W. Bush prevailed, essentially giving him the presidency. The current issue raises important constitutional questions, but also involves race and nasty partisan politics. At least 35 political and advocacy groups have filed amicus briefs supporting one side or the other.

The appeals involve an Indiana law, passed by the Republican-controlled legislature in 2005, requiring that a voter present a photo ID when casting a ballot in person. Previously, citizens needed only to sign a poll book to vote.

In oral arguments Wednesday, Paul Smith, attorney for a coalition of groups and voters, including the NAACP and the Democratic Party, told the high court the state law "directly burdens over our most fundamental rights, the right to vote."

Smith faced tough questions from most of the high court bench.

Justice Antonin Scalia wondered why the Democrats were the ones filing the lawsuit, saying it should have been filed by individual voters who may have been directly harmed by the law. His questioning suggested he thought the case had more to do with politics than the law.

Justice Anthony Kennedy pressed Smith repeatedly to show that the law caused a real burden.

"You want us to invalidate the statute because of minimal inconvenience?" he asked.

Kennedy's vote could prove crucial, and he seemed to want to uphold the Indiana statute, perhaps with some changes.

Lawyers on both sides presented conflicting data on just how many voters would be affected. Democrats said as many as 400,000 people in Indiana do not have the required identification to vote, while state officials countered the number is fewer than 25,000, perhaps only several thousand.

Chief Justice John Roberts, himself an Indiana native, took issue with assertions that the reasons given for passing the law in the first place had little factual basis.

"If somebody wins an election by 500,000 votes, you may not be terribly worried if some percentage were cast by fraud, but you might look to the future and realize there could be a closer election and ... because it's fraud, it's hard to detect," he said.

Roberts also pointed out the state provides free photo IDs to anyone who requests one to vote. "They (the state) help you get it," he said tartly. "If you don't have a photo ID, come in and we'll give you one."

The state's top lawyer, Indiana Solicitor General Thomas Fisher, faced pointed questions from several more liberal justices.

Fisher said not a single voter could show they had been adversely affected by the law, despite six elections held since the law passed two years ago. He said the number affected would be "infinitesimal."

But Justice Ruth Bader Ginsburg said that was beside the point, and the legal questions should be settled before the fall elections take place.

"The horse is going to be out of the barn. They will have the election, and just what they are afraid of could happen, that the result will be skewed in favor of the opposite party, because there are people who have not been able to vote," she said. "They are in this bind after the election. They've already lost that one."

Breyer wondered whether there "was a less restrictive way to get an ID."

A national panel headed by former President Jimmy Carter and former Secretary of State James Baker said photo IDs are beneficial, especially one just for voting. The justice seemed to endorse the idea.

"That less restrictive way would satisfy your anti-fraud interest much better than the way you have chosen," Breyer told Fisher. "That photo proves that Mr. Smith who comes in and asks for it is the same Mr. Smith who registered to vote. And that's all your system does in the first place."

Justice John Paul Stevens noted the law in question was passed by a GOP-controlled legislature and signed by a Republican governor.

He said candidly that the law would "have an adverse affect on Democrats."

Indiana's law had been upheld by a federal appeals court. State and federal courts around the country have issued conflicting rulings on voter ID laws. Missouri's law was found unconstitutional, but similar ones in Georgia, Arizona and Michigan were found to be proper.

State laws on voter identification vary widely, with Indiana's and Georgia's considered the most restrictive. Nearly all states require a photo identification when people first register to vote.

The Supreme Court already has heard two election-related appeals this term. One involves Washington state's open primary system, and the other is a dispute over the selection of state judges in New York.

A ruling in the Indiana case is expected by late June, in time, perhaps, for states to revise their laws for the November elections, if required.E-mail to a friend